1. Field of the Invention
The present invention relates to an optical/mechanical method of controlling the gap between a metal-casting crucible orifice and an adjacent chill surface.
2. Description of the Prior Art
In the process of flow casting of liquid alloys to obtain glassy metal strip, the spacing between crucible orifice and casting wheel surface has to be closely controlled in order to obtain homogeneous strip. High temperatures and surface speeds in this region rule out conventional contact-type measuring devices and, instead, necessitate remote measurement and control.
Zanoni in U.S. Pat. No. 3,853,406 discloses a differential, optical, non-contacting diameter gauge utilizing a pair of linearly scanning light beams sequentially scanning the test piece. The two parallel, offset scanning laser beams are produced by reflecting two laser beams, separated by a preset angle, from a uniformly rotating mirror or multifaceted prism placed at the focus at a lens.
Zanoni in U.S. Pat. No. 3,961,838 discloses an apparatus for producing a scanning laser beam of constant linear velocity by reflecting a laser beam from a uniformly rotating mirror.
Zanoni in U.S. Pat. No. 3,856,411 discloses an optical device in which a beam of laser light is reflected from a rapidly oscillating mirror and scanned across a test object to determine the diameter of the test object.
Barker et al. in U.S. Pat. No.4,101,612 disclose an optical method and apparatus for measuring stress relaxation, including monitoring the dimensions of a material (extrudate) using optical means for scanning the extrudate. Their apparatus measures the diameter of a strand as it passes within an aperture.
Parkinson in U.S. Pat. No. 3,829,220 discloses a "profile gauge," which measures the width of an object by scanning two beams across the object.
Loy in U.S. Pat. No. 3,992,017 discloses an apparatus and method for detecting, measuring, and controlling the preselected width of a continuously moving web of material. The apparatus may include optical position sensing together with feedback control.
Other optical, non-contact measurement schemes have been disclosed by Dehait, in U.S. Pat. No. 4,097,158, Petrohilos, in U.S. Pat. No. 3,765,774, and Asar et al., in U.S. Pat. No. 3,854,052.
None of the methods and apparatus of the prior art have been directed to the unique problems posed by maintaining the gap between a metal-casting crucible orifice and an adjacent chill surface.